Digital lighting technologies, i.e. illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications. Some of the fixtures embodying these sources feature a lighting module, including one or more LEDs capable of producing different colors, e.g. red, green, and blue, as well as a processor for independently controlling the output of the LEDs in order to generate a variety of colors and color-changing lighting effects, for example, as discussed in detail in U.S. Pat. Nos. 6,016,038 and 6,211,626.
Lighting units of all types have an expected lifetime, and sooner or later will fail. Sometimes the failure is sudden (e.g. incandescent lamps), or it is gradual (e.g. fluorescent lights or LED-based light sources). Failed lighting units are often a problem for numerous reasons. The lack of sufficient illumination could result in a safety hazard, an unsightly illumination zone or a spoiled shop display which may deter potential customers.
A failed lighting unit needs an appropriate remedial action, i.e., either to be replaced or fixed. But often, a spare lighting unit is not readily available, or it is inconvenient to replace or fix the lighting unit right away. This can result in no illumination for an undesirably extended period of time. This scenario can be more likely for LED-based lighting units, as users may not keep spares on account of their higher costs and longer lifetimes. This problem may be overcome by providing a warning signal indicating that remedial action is required imminently.
Faults in the operation of a lighting unit include, but are not limited to, an excessive temperature, a low light output, a high drive current or voltage, a low fan speed, a high current for driving a fan, or an excessive change in temperature, or rate of change of temperature. Other faults include failure of sensors and/or hardware, software bugs and “divide by zero” errors in firmware, or other faults readily known to skilled artisans.
In many cases, a lighting unit fails as a result of the malfunction or failure of one or a few of its component modules. In such a scenario, an appropriate remedial action is to replace or fix the specific failed component module(s), rather than replace the entire lighting unit. Some conventional lighting systems employ means for indicating imminent failure. However, as these systems are typically configured to only indicate a general failure of the entire lighting unit, they are poorly suited to ascertain an appropriate remedial action, without further fault tracing.
For example, the COLORBLAST POWERCORE luminaire available from Philips Color Kinetics (Burlington, Mass.) is configured to output a dull red light in the case of overheating. However, there is no indication as to the cause of overheating, whether it is due to internal malfunction, poor installation, end of lifetime or a high ambient temperature. Therefore, remedial options are to replace the entire lighting unit outright or to attempt to determine a cause for the overheating via active fault tracing on the lighting unit.
As a further example, lighting units, particularly those recessed in ceilings, generally dissipate waste heat via conduction to the surroundings. Often, ceilings are insulated and therefore impede the loss of heat. Excessive temperatures may reduce the lifetime of light sources and a fan or other kind of active cooling system is typically incorporated in the lighting unit to improve heat dissipation. The lifetime of a fan may however, be less than the lifetime of the light sources. The fan's performance may deteriorate due to dust build up, and may only need removal and cleaning, or other maintenance, instead of replacement. Identical lighting units may suffer vastly different dust buildups depending on the environment they are installed in. If a warning signal only indicates an imminent general failure of the lighting unit, it is likely that a lighting unit with functional components is unnecessarily completely replaced, considering, for example, that complete replacement may be more cost effective than having a technician performing diagnostic testing.
Thus, there is a need in the art to provide systems and methods for providing warning signals for a lighting unit that will visually indicate to a user the specific nature of a fault, allowing for determination of an appropriate remedial action. It is also desirable to communicate or display these warning signals to the user in a cost-efficient and effective manner.